Spin Ice - A Magnetic Analogue of Common Water Ice with Emergent Electrodynamics with Deconfined and Fractionalized Excitations

Discovered in 1997, spin ices are frustrated magnetic materials that display a low-temperature state characterized by a nonzero residual magnetic entropy that is intimately related to the proton disorder entropy of common water ice, first rationalized by Linus Pauling in 1935 – hence the name spin ice. In this talk, I will review the salient aspects of these fascinating systems that have sustained the interests of theorists and experimentalists alike for twenty years. In particular, I will emphasize the many layers of "strong emergence" that these systems harbour and comment on their field-theoretic description akin to that of quantum electrodynamics on the lattice with deconfined "matter" excitations and the accompanying gauge boson.